The mammals have figured out that fish are easy prey at Bonneville Dam, where chinook and steelhead gather as they attempt to navigate fish ladders on the way to upriver spawning areas.

According to the U.S. Army Corp of Engineers, 4,243 salmon and steelhead were eaten by sea lions last year in the area immediately below the dam. This is the highest number consumed to date.

Although California sea lions are protected by federal law, there is concern that they are threatening fish populations before they get the opportunity to spawn.

“As wildlife managers, we have a responsibility to do what we can to protect vulnerable fish runs,” said Guy Norman, southwest regional manager for the Washington Department of Fish and Wildlife. "California sea lions -- some weighing more than 1,000 pounds -- can literally eat their weight in salmon and steelhead in a couple of months below Bonneville Dam.”

The Humane Society of the United States is against the culling of sea lions, countering that fishermen and dams on the Columbia and Snake rivers kill more fish than the sea lions do and that cutting back salmon catch allowances could easily make up for the amount of fish eaten by the mammals.